It is commonplace in the construction of residential houses to install batt or particulate insulation between the ceiling joists of the house attic. However, problems may arise if the insulation is installed around the perimeter of the attic between the ceiling joists and the overlying roof deck to such an extent that air vents are blocked. Building codes in most jurisdictions presently require a free flow of ventilating air above the insulating material in order to cool the attic space during the summer months and restrict moisture buildup in the winter.
Soffit or eave vents are currently the most common type of residential attic ventilation. Such vents are intended to provide free flow of air through the opening between the top wall plate of the house and the underside of the roof deck. Ventilating air can circulate into and out of the attic cavity provided that this passageway remains unobstructed.
The need to have a ventilating passageway above the insulating material presents several problems. Excessive heat loss may result if ventilating air is permitted to flow freely through the attic. The thermal value of insulating material decreases dramatically if there is not dead air space above the insulating material to provide resistance to the conductive flow of heat.
Another problem which has arisen is the tendency of particulate insulating material to fall through the opening between the top wall plate of the house and the roof deck into the soffit space. Common practice today is to install cardboard or polystyrene vents in this opening and then stuff fibreglass insulation between the rafters and the vents above the top plate in order to act as a physical barrier. Particulate insulation is then blown into the attic cavity between the ceiling joists.
Although such fibreglass barriers prevent insulation from falling into the soffit space, they do not effectively restrict airflow. Consequently, the entire perimeter of the house between the top wall plate and the roof deck has very little insulating quality and no measurable R values. This allows for significant heat loss and may result in condensation problems in the attic.
The present invention is directed to a cardboard baffle which can be installed between adjacent roof rafters to regulate the flow of ventilating air into and out of the attic. One aspect of the invention is an insulation stop which can be installed between the top wall plate and the roof deck to act as a rigid air barrier and to prevent particulate insulation from inadvertently falling into the soffit. A second aspect of the invention is a ventilation baffle which can be installed between adjacent roof rafters to ensure that a ventilating passageway is maintained above the insulating material. Both configurations of the baffle preserve a dead air space above the insulating material by restricting airflow through the lower portion of the attic cavity adjacent the ceiling joists.
The insulation stop and ventilation baffle of the present invention are companion products which may be readily installed in combination to result in optimal attic ventilation, while at the same time maximizing the thermal value of the attic insulation.
Several insulation vents and baffles are disclosed in the prior art. U.S. Pat. No. 4,069,628 granted to Kreimer on Jan. 24, 1978 discloses an eave thermal baffle which can be installed between adjacent roof framing members. The baffle is constructed from a blank having a series of score lines or creases which define separate panels and flaps. The baffle blank can be bent about the score lines and installed to provide a trough for the passage of air from the eave-soffit area into the attic.
U.S. Pat. No. 4,189,878 granted to Fitzgerald on Feb. 26, 1980 also discloses a house roof insulation vent which is attachable between adjacent roof rafters. The vent consists of a generally rectangular sheet made of corrugated cardboard or the like. Each sheet has a series of crease lines which enable the sheet to be folded into hingedly connected sections and installed between the roof rafters of the house. Once installed, the invention creates a passageway for free flow of ventilating air from the eave or soffit area along the interior base of the roof boards into the attic cavity. Other combined insulation stops and ventilation baffles are disclosed in U.S. Pat. No. 3,863,553 issued Feb. 4, 1975 to Koontz and U.S. Pat. No. 3,160,987 issued Dec. 15, 1964 to Pinkley.
The above-noted prior art references have several apparent shortcomings. The principal drawback of the Kreimer baffle is that it is designed to fit between roof rafters having a standard spacing and a single truss heel size. Accordingly, it cannot be readily adapted to suit alternative framing sizes. The Fitzgerald baffle also has crease lines and flaps which are fixed at a standard size and therefore it is similarly unsuitable for adaptation to non-standard construction dimensions.
The present invention, by contrast, incorporates a series of strategically placed perforated crease lines and preprinted cut and score lines to allow adjustment of the width and height of the baffle to suit the dimensions of the particular job. For example, the present invention can be readily adapted for installation in houses having 12 inch, 16 inch or 24 inch rafter spacing, as well as a number of truss heel sizes.
Furthermore, unlike the Kreimer and Fitzgerald references, one aspect of the present invention also includes a further element which completely blocks the flow of air between the top wall plate of the house and the roof deck. This configuration completely avoids the possibility that particulate insulation could inadvertently fall through the openings located around the periphery of the attic into the soffit space. Used in conjunction with the ventilation baffle, it improves the isolation and containment of the insulation material. U.S. Pat. No. 3,240,144 issued Mar. 15, 1966 to Lind discloses a baffle consisting of a rectangular plate forming a dam to contain the insulation, but this baffle is designed to allow air to flow over the top of the baffle.